The present invention relates generally to novel pharmaceutical compositions of matter comprising diphenhydramine and one or more non-steroidal anti-inflammatory drugs (NSAID) having analgesic and anti-inflammatory properties, and to methods of using said compositions to elicit an enhanced analgesic or anti-inflammatory response in mammalian organisms in need of such treatment.
Non-narcotic analgesics, most of which are also known as non-steroidal anti-inflammatory drugs (NSAID), are widely administered orally in the treatment of mild to severe pain. Within this class, the compounds vary widely in their chemical structure and in their biological profiles as analgesics, anti-inflammatory agents and antipyretic agents. Aspirin, acetaminophen and phenacetin have long been among the most commonly used members of this group; more recently, however, a large number of alternative non-narcotic agents offering a variety of advantages over the earlier drugs have been developed. Tolernce or addiction to these drugs is not generally a problem with their continuous use in the treatment of pain or in the treatment of acute or chronic inflammatory states (notably, rheumatoid arthritis and osteoarthritis); nevertheless, these drugs generally have a higher potential for adverse side-effects at the upper limits of their effective dose ranges. Moreover, above each drug's upper limit or ceiling, administration of additional drug does not usually increase the analgesic or anti-inflammatory effect. Among the newer compounds in the non-narcotic analgesic/nonsteroidal anti-inflammatory group are compounds such as diflunisal (Dolobid.RTM.), zomepirac sodium (Zomax.RTM.), ibuprofen (Motrin.RTM.), naproxen (Naprosyn.RTM.), fenoprofen (Nalfon.RTM.), piroxicam (Feldene.RTM.), flurbiprofen, mefenamic acid (Ponstel.RTM.) and sulindac. See also Physicians' Desk Referenoe, 35th edition, 1981, and The Merck Index, ninth edition, Merck & Co., Rahway, N.J. (1976), for information on specific nonsteroidal anti-inflammatory agents. Also see, generally, Wiseman, "Pharmacological Studies with a New Class of Nonsteroidal Anti-Inflammatory Agents--The Oxicams--With Special Reference to Piroxicam (Feldene.RTM.), The American Journal of Medicine, Feb. 16, 1982:2-8; Foley et al, The Management of Cancer Pain, Volume II--The Rational Use of Analgesics in the Management of Cancer Pain, Hoffman-LaRoche Inc., 1981; and Cutting's Handbook of Pharmacology, sixth edition, ed. T. Z. Czaky, M.D., Appelton-Century-Crofts, New York, 1979, Chapter 49:538-550, including structural formulas for representative group members.
Diphenhydramine[2-(diphenylmethoxy)-N,N-dimethylethylamine]is also a well-known therapeutic agent in long standing use by clinicians as an antihistamine. It is recognized in both the U.S.P. and N.F. as an official antihistamine of the ethanolamine (or aminoalkyl ether) type and is available as the hydrochloride salt in Benadryl.RTM. and various alternative sources in 50 milligram delayed action tablets, 25 and 50 milligram capsules, elixirs (12.5 mg/5 ml) and sterile solution for injection (10 mg/ml). Depending upon the therapeutic indication, diphenhydramine is recommended in single or divided doses of between 12.5 to 50 milligrams with a maximum daily dosage not to exceed 300 milligrams. The antihistaminic activity of diphenhydramine is directly attributable to its competition with histamine for cell receptor sites on effector cells although diphenhydramine also demonstrates, in addition, a number of therapeutic applications attributable to central actions unrelated to histamine antagonism. Antihistaminic indications for diphenhydramine include perennial and seasonal allergic rhinitis, vasomotor rhinitis, allergic conjunctivitis, urticaria and as adjunctive therapy for anaphylactic reactions. Central nervous system side effects (non-histaminic actions) which have been capitalized upon include prophylactic and active treatment of motion sickness and, more broadly, as an antinauseant and in the treatment of mild forms of Parkinsonism. Diphenhydramine demonstrates both stimulant and depressant effects on the central nervous system although stimulation is only occasionally seen in patients given conventional doses with accompanying restlessness, nervousness and inability to sleep. The more predominant sedative action of diphenhydramine has been beneficially capitalized upon with the usage of diphenhydramine as a somnolent when employed at the maximum 50 milligrams dose in both prescription and over-the-counter forms. In this regard, it is noted that the Food and Drug Administration announced in the November 1983 FDA Drug Bulletin (Vol. 13, No. 3) that diphenhydramine (50 mg.) may now be marketed over-the-counter as a nighttime sleep aid.
An early study (1958) investigated the properties of diphenhydramine as a pre-anesthetic medication. (Lear, et al., "Comparative Studies of Tranquilizers Used in Anesthesia." JAMA, 1958, 166(12): 1438-1443). The authors concluded that diphenhydramine, particularly when used in combination with meperidine, provides beneficial preoperative sedation with less overall depression than previously experienced with the use of routine doses or narcotics and barbiturates.
Diphenhydramine has also been investigated with varying results with respect to its potential as a weak analgesic. Diphenhydramine hydrochloride when introduced intravenously has been reported as being useful in obstetric analgesia alone and in combination with alcohol. See Cappe, B. E. et al, "Recent Advances in Obstetric Analgesia", JAMA, 1954, 154(5); 377-379. Campos et al in a comparative study found that diphenhydramine given either orally or intramuscularly could not be distinguished from placebo in patients with postoperative fractures or somatic pain ["The Analgesic and Hypothermic Effects of Nefopam, Morphine, Aspirin, Diphenhydramine and Placebo", Journal of Clin. Pharmacology, January, 1980, pp. 42-49.]
Albal and Chandorkar studied an injectable combination analgesic consisting of analgin 375 mg, a centrally acting analgesic, diazepam 2.5 mg, and diphenhydramine 20 mg, and found relief from pain. They did not, however, study the unique contribution of diphenhydramine. [Albal, M.V., and Chandorkar, A.G. "Clinical Evaluation of Sedyn-a-Forte, an Analgesic Injection Containing Analgin, Diphenhydramine and Diazepam." Indian Journal of Ophthalmology, 1982, 30:271-273]. [Note: analgin referred to in the foregoing study is dypyrone; see The Merck Index, p. 3361, 1976.]
While diphenhydramine has been investigated with respect to its weak analgesic properties, it is also evident from the foregoing that its sedative and local anesthetic properties may, in part, account for its suspected potential for relieving pain. In the Lear et al, supra, study diphenhydramine at 25 to 50 milligram doses was insufficient as a preanesthetic medication and combination with meperidine (a narcotic analgesic) was proposed to optimize the potential beneficial effects of diphenhydramine as an analgesic.
Hydroxyzine, which is a minor tranquilizer with antihistaminic activity, has been evaluated as an analgesic. Beaver and Feise found that, "This study unequivocally demonstrates analgesic activity for a 100 mg dose of intramuscular hydroxyzine in the general range of that produced by 8 mg of morphine. In addition, the analgesic activity of hydroxyzine appears additive with that of morphine when the two drugs are given together." The findings of the study do not indicate synergistic activity. (Beaver, W. T. & Feise, G. "Comparison of the Analgesic Effects of Morphine, Hydroxyzine, and Their Combination in Patients with Postoperative Pain." Advances in Pain Research and Therapy, 1976, 1:553-557)
Only recently have animal studies been conducted in which the analgesic activity of diphenhydramine has been investigated. Bluhm, et al., in a study conducted on mice, found that diphenhydramine potentiates morphine, a centrally acting drug, when administered parenterally. Oral administration of drugs was not studied. (Bluhm, et al., "Potentiation of Opioid Analgesia By H.sub.1 and H.sub.2 Antagonists." Life Sciences, 1982, 31:1229-1232).
Diphenhydramine has not been heretofore proposed for use in combination with any of the newer nonsteroidal analgesic/anti-inflammatory agents (i.e., excluding aspirin, acetaminophen and phenacetin). In U.S. Pat. No. 4,420,483 issued Dec. 13, 1983, the present applicants disclose the hastening of the onset of analgesic and anti-inflammatory responses observed with several different nonsteroidal anti-inflammatory agents as well as the enhancement of the analgesic and anti-inflammatory response with such agents by the concomitant administration of caffeine as a potentiating adjuvant.
Applicants have now surprisingly found that diphenhydramine synergistically enhances the analgesic and anti-inflammatory properties of such non-steroidal anti-inflammatory drugs (NSAID).